London — Cancer patients have been left free of the disease after being treated with a new drug that harnesses the power of their own immune system.

Four out of 38 patients with non-Hodgkin’s lymphoma saw the disease disappear after treatment, while five others saw reductions of 50% in their tumors.

The drug, which could be cheaper than other similar therapies, works by activating the body’s own defenses to attack the cancer.

The results have been described as a significant development in the use of immunotherapy, the process of using the body’s own immune system to fight disease. While the trials were only carried out on patients with the blood cancer, it is hoped the method can be adapted to tackle other cancers.

Cancer Research UK’s chief clinician, Peter Johnson, described the preliminary results as “exciting.”

“Although the side effects need to be monitored carefully, we hope that this type of treatment will prove to be active in larger trials in the future,” he said.

Earlier this year doctors announced that a patient with advanced skin cancer was free of the disease two years after they injected him with billions of his own immune cells using a different method. However, experts warned at the time that the process could prove extremely expensive.

The development of the drug could prove a much cheaper alternative way of providing immunotherapy treatments.

“This a significant study,” Dr. Cassian Yee from the Fred Hutchinson Cancer Research Center in Seattle, who has had significant results using the alternative method of treating patients with white blood cells grown in the lab, said.

“It remains to be seen if most of the responses are long lasting. Certainly the results are very promising.”

The drug, which has been developed by Micromet, in Bethesda, Md., was trialled by a team led by Dr. Ralf Bargou at the University of Wurzburg in Wurzburg, Germany. Of the 38 patients with non-Hodgkin’s lymphoma who took part, two of the seven on the highest doses saw their cancer disappear while five others saw reductions in tumor size of more than 50%.

One patient on a lower dose also became cancer-free and remains so after more than a year.

The results, published yesterday in the journal Science, are encouraging because they suggest that the bigger the dose, the bigger the effect.

The study’s co-author, Dr. Patrick Baeuerle, of Micromet, said all seven who received the highest dose responded to the drug.

There are adverse side effects involved, however, such as fevers and chills, though all stopped after treatment ceased.

A further trial is investigating how the drugs works in patients with another form of blood cancer, called acute lymphoblastic leukaemia.